1. Field of the Invention
This invention generally relates to electrical switching devices and more particularly to multiple pole switching devices of the dual in-line package type.
2. Description of Related Art
Dual in-line package (DIP) switches have many applications, particularly in electronic circuitry used in digital data processing systems and like products. DIP switches comprise a plurality of single-pole, single-throw switching mechanisms physically located in a unitary package. Two parallel rows of terminals, or terminal pins, connect switching mechanisms inside the package to circuits on a printed circuit board. Each switching mechanism makes or breaks a circuit between a pair of terminals constituted by a corresponding terminal in each row.
Typically a DIP switching mechanism comprises at least one stationary contact inside the switch package. Usually this contact is formed integrally with a first terminal. A movable contact inside the package may be constructed integrally with the second terminal. It may also be independent and engage a second stationary contact that is integral with the second terminal. An actuating mechanism is accessible to an operator and shifts the movable contact to make or break a conductive path between the corresponding terminals. Normally this occurs when the actuating mechanism overcomes a bias that forces the movable contact to an open circuit condition.
Over time certain DIP switch characteristics have become required or desireable. For example, it is very desirable that actuator movement be accompanied by a definite detent action to assure an operator that the switch either is open or closed (i.e., is "off" or "on"). DIP switches should be small to increase component denstiy. They must be reliable and easy to use. Finally, they should be inexpensive to manufacture. A number of switch constructions have been proposed in an attempt to provide all of these characteristics.
U.S. Letters Pat. No. 3,291,951, for example, discloses a miniature single-pole, double-throw switch. A common movable contact rotates to make an electrical connection with one of two stationary contacts. A slot in a rotary actuator indicates which switching connection has been made.
U.S. Letters Pat. No. 3,900,709 discloses a multiple switch assembly having independent operators that rotatably cam discrete leaf spring type contact assemblies. In this switching device, a first terminal and stationary contact are formed as an integral assembly. A second contact is formed on a transverse extension to a second terminal. The terminal and extension are manufactured such that there is a spring bias exerted to separate the two contacts. Turning a rotary actuator cams it along a vertical axis to overcome the bias of the second contact and displaces it into connection with the first contact. A slot in the rotary actuator and a detent indicate switch operation. A radially extending pin on the actuator engages a recesses in the opened and closed positions to provide the detent operation.
U.S. Letters Pat. No. 3,944,760 discloses a switch assembly having an insulating slider actuator inserted between normally closed contacts. Each of two terminals extends into a switching cavity and bends to provide overlying relationship between the contacts. One of the contacts is biased into contact with the other. A slide, cantilevered around the other contact, moves between the two contacts to separate them and open the switch. In the other position, the insulating slide is removed so the contacts make an electrical connection. A cam surface on the end of the slider passes over an acutely formed can follower on the movable contact to provide a detent.
U.S. Letters Pat. No. 4,117,280 discloses a miniature DIP switch utilizing a rocker actuator. A first terminal and integral stationary contact are inside a switching cavity. A second terminal has a long cantilevered arm with a contact at its free end. Internal stresses in the second contact normally maintain an open-circuit condition. The rocker actuator has a depending cam surface that moves against a cam follower portion on the second contact. This forces the contacts into electrical connection. Over-center springs between the base unit and the rocker provide a detent action.
U.S. Letters Pat. No. 4,119,823 also discloses an electrical switch of the dual in-line package type. Each of two terminals extending from the switch end into overlapping contacts inside a switching cavity. When a rotary actuator moves from an opened to a closed position, it cams one contact into the other. The camming surface rides over a curved contact portion to provide a detent.
U.S. Letters Pat. No. 4,412,108 discloses a switch having two terminals extending into a switching cavity with spaced stationary contacts. A movable contact pivots on a first stationary contact to produce an electrical connection with the second contact. A rocker actuator with a spring-biased cam moves to opposite sides of the movable contact pivot during switching operations. When the cam is on the same side of the pivot as the second contact, it forces the movable contact into an electrical connection. An embossment on the movable contact at the pivot point forces the cam upward as the cam passes over the pivot. Then the cam extends as it passes over this embossment to provide a detent action.
Each of these references, taken singly or in combination, provide various switching mechanism that are characterized by overly complex actuators, contact arrangements that are difficult to manufacture or an excessive number of components. In some, manufacturing tolerances must be tightly controlled to maintain switch operation and this can increase manufacturing costs.
Therefore, it is an object of this invention to provide a switching device of the dual in-line package type that is particularly adapted for electronics applications.
Another object of this invention is to provide a switching device of the dual in-line package type with improved reliability achieved through a reduction in a number of components.
Still another object of this invention is to provide a switching device of the dual in-line package type in which manufacturing is simplified by reducing the number of components.
Still another object of this invention is to provide a switching device of the dual in-line package type in which modular construction techniques can be used to simplify manufacturing, reduce manufacturing costs and minimize inventory requirements.